The three-wire ultrasonic level transmitter is the compact solution for non-contact continuous level measurement in process vessels, storage tanks and open channels. The transmitter also features a built-in 10A relay which can be configured as an alarm on a single set point or latched on two different set points for automatic fill or empty operations. Industrial and municipal liquid examples include sodium hydroxide, wastewater, resin, wax, liquor and bleach. An ultrasonic sound wave is pulsed eight times per second from the base of the transducer. The sound wave reflects against the process medium below and returns to the transducer. The microprocessor based electronics measure the time of flight between the sound generation and receipt, and translates this figure into the distance between the transmitter and process medium below. The surface of the level being measured must be free of fumes, vapors, foam and the surface must be flat; the signal may be lost if any of these conditions are present.